Metadata Report for BODC Series Reference Number 1364251

• Metadata Summary

• Problem Reports

• Data Access Policy

• Narrative Documents

• Project Information

• Data Activity or Cruise Information

• Fixed Station Information

• BODC Quality Flags

• SeaDataNet Quality Flags

Metadata Summary

Problem Reports

No Problem Report Found in the Database

RRS James Cook (JC079) AMT22 Atmospheric OVOC Mixing Data Quality Report

The data were quality controlled by the originator before being received by BODC and no further issues were identified with the final submitted dataset.

Data Access Policy

Open Data supplied by Natural Environment Research Council (NERC)

You must always use the following attribution statement to acknowledge the source of the information: "Contains data supplied by Natural Environment Research Council."

Narrative Documents

RRS James Cook (JC079) AMT22 Atmospheric OVOC Mixing Instrument Documentation

The following table shows the instrument used:

RRS James Cook (JC079) AMT22 Atmospheric OVOC Mixing Ratios Data Processing Document

Data collection, measurements and originator's processing

Concentrations of atmospheric Oxygenated Volatile Organic Compounds (OVOCs) were quantified by a protontransfer-reaction mass spectrometer (PTR-MS) located in the meteorological lab. The PTRMS performed well during the cruise, with good sensitivity and without any notable issues, even in rough weather. For around 19 hours per day, the PTR-MS operated under atmospheric mode and continuously measured at ~2.1 Hz. Air was drawn in from the meteorological platform above the bow via ~25 m of quarter inch internal diameter PFA tubing by a vacuum pump. For most of the cruise, methanol, acetone, and acetaldehyde were measured simultaneously. Between 3^rd and 16^th November 2012, only methanol and acetone were measured because the level of acetaldehyde was near the instrument's detection limit. Dueterated methanol and acetone gas standards were injected continuously into the inlet line. The standard flow was regulated by a digital thermal mass flow controller. Ambient concentrations of those OVOCs were then calculated from the ratio of the natural and dueterated signals. The use of dueterated standards minimizes uncertainties due to instrumental drift and variable efficiencies. Background values were taken by directing ambient air through a catalytic converter, which removes organic compounds, for two minutes at the top of every hour. A plastic funnel, initially attached to the front of the inlet, was found to emit contaminants at the mass to charge ratios of acetaldehyde and acetone (m z^-1 45 and 59 respectively). This contamination was most severe under direct sunlight and under high temperature. The funnel was removed on 29^th October 2012 and the problem disappeared thereafter. However, acetaldehyde and acetone air concentrations before 29^th October 2012 were highly uncertain. For that period, the daytime data were discarded, when the contamination was the most severe, and the nighttime data were corrected by detrending with temperature, methanol was unaffected. The hourly averaged concentrations are included here. To remove the influence of ship's exhaust, only the relative wind direction sector between -110° to +110° and relative wind speed over 2 m s^-1 are retained. More information may be found in Yang et al., 2014.

BODC Data Processing

The data were submitted to BODC in teb-delimited text format consisting of Date and Time, Latitude, Longitude, Atmospheric methanol mixing ratio, Atmospheric acetaldehyde mixing ratio and Atmospheric acetone mixing ratio. The data were then transferred to the BODC format and loaded to the database. Parameter codes defined in the BODC parameter dictionary were assigned to the variable as shown in the table below:

Screening

The data was csreened using the in-house software Edserplo. The data was considered to be of good quality and no additional flags were applied.

References

Yang, M., Beale, R., Liss, P., Johnson, M., Blomquist, B. and Nightingale, P. (2014). Air-sea fluxes of oxygenated volatile organic compounds across the Atlantic Ocean. 14, 8015-8061, doi:0.5194/acpd-14-8015-2014

PDZ Europa 20-20 isotope ratio mass spectrometer

The 20-20 isotope mass spectrometer brochure was not available however, based on evidence from other websites and the 20-22 mass spectrometer brochure the key features are very similar and are as follows:

120° extended geometry with an 11 cm radius magnetic sector giving an effective 21 cm radius dispersion and double direction focusing. Additional high dispersion long spur with 98.8° sector which creates a distance of 24 cm between the focal points for m/z 2 and 3. This leads to an abundance sensitivity at m/z 3 of <1 ppm which eliminates helium tailing in to the D/H collector.

Truly universal Faraday triple collectors for simultaneous collection of adjacent masses in the range 28,29,30 - 64,65,66 with no adjustment of collectors or amplifiers. Additional single Faraday collector and high gain amplifier for m/z 3 on the hydrogen spur.

The desired combination of the 4 collectors is selected through the software. Software switchable variable gain amplifiers and 50v amplifier outputs are available as options.

Optional extended geometry system to incorporate up to 12 collectors for custom applications.

Asymmetric extended geometry to give true stigmatic focussing with twice the dispersion of normal geometry with the same radius sector.

Shorter path length than traditional extended geometry to decrease ion/molecule interactions and so ensure 100% transmission through the analyser and a sensitivity which is higher than any other commercial IRMS (<1000 molecules/ion for CO₂).

Small analyser footprint and wide flat peak shape reduce the effect of temperature drift therefore removing the need for peak centring during analysis.

Design allows greater tolerance of the known variables of ion optics making the manufacture of the analyser more reproducible and less sensitive to magnet positioning.

True differential pumping by turbo-molecular pumps with a high compression ratio for both He and H2, to remove the detrimental effect of abundance sensitivity during continuous flow applications and eliminate memory.

With a mass range covering 2 to 96 AMU it is suitable for the analysis of light stable isotopes in all the commonly measured gases; H₂, N₂, NO, N₂O, O₂, CO, CO₂, SO and SO₂.

Triple port reference gas injection system. Suitable for calibrating each sample, using a reference gas instead of an internal standard and for easy tuning of the mass spectrometer. Size, type and positioning of reference gas pulses are under software control.

Data acquisition system uses state of the art highly stable and linear high frequency converters which produce integral slices with zero dead time and quantisation below the beam statistical noise floor at all signal levels.

The 20-22 isotope ratio mass spectrometer brochure may provide more information.

PDZ Europa ANCA GSL Sample Preparation Unit

The ANCA-GSL is a combined elemental analyser and gas purification module which produces clean gas samples for a 20-22 or GEO series isotope ratio mass spectrometer. The ANCA-GSL module allows samples such as soil, viscous liquids, plant material and organic compounds, to be analysed directly by utilizing Dumas combustion for ¹⁵N, ¹³C and ³⁴S or pyrolysis for ¹⁸O and D. It also allows isotope analysis of abundant gases from septum sealed containers. During combustion mode, a capsule containing the sample falls into the combustion tube and is converted in the presence of oxygen to CO₂, N₂, NO_x and H₂O. An elemental copper stage reduces NO_x, a MgClO₄ trap removes water vapour, a switchable Carbosorb trap can be used to remove CO₂ (for ¹⁵N only analyses) and a GC column separates CO₂ from N₂ (allowing dual isotope analysis). Modified packings, a Nafion dryer and different GC column allow ³⁴S analysis. During pyrolysis mode, a capsule containing the sample falls into the pyrolysis tube containing glassy carbon grit. The pyrolysis products, CO, N₂, and H₂ are purified by chemical processes. A MgClO₄ trap removes water vapour, a Carbosorb trap removes any CO₂ (minor by-product of the reaction) and a GC column separates CO from N₂. The gas analysis facility of the ANCA-GSL is provided by an automated sampling needle and the gas chromatograph part of the module. N₂, CO₂ and O₂ can be analysed at atmospheric concentrations while H₂, SO₂, N₂O, CO₂ and NO can be measured at elevated levels e.g. from a head space, water equilibrations, continuous flow carbonate measurements and DIC analyses.

More information on the precision may be found in the ANCA GSL brochure.

Project Information

No Project Information held for the Series

Data Activity or Cruise Information

Cruise

Complete Cruise Metadata Report is available here

Fixed Station Information

No Fixed Station Information held for the Series

BODC Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle:

SeaDataNet Quality Control Flags

The following single character qualifying flags may be associated with one or more individual parameters with a data cycle: